Allosteric enzymes in biosynthetic pathways are often inhibited by the binding of a ligand. The ligand often: explain how you got the answer  a.binds the active site b.is a precursor metabolite c.is the end product d.is ATP

A histidine was determined to be the critical residue involved in an enzyme-catalyzed reaction. If the pKa of the histidine is known to be 6.5 in the active site and the pH of maximum catalytic activity is 7.2, what is likely the primary role of histidine in the catalytic reaction?  A. forms a covalent bond with the substrate B. reduces the entropy of the substrate C. stabilizes a charged intermediate D. acts as a proton donor   Aspartate and lysine are in the active site of an enzyme. They are both known to participate directly in catalysis. The pKa's of the residues are found to be 3.2 and 9.6, respectively for aspartate and lysine. The optimum pH for the enzyme is 6.4. Which forms of these two residues will predominate when the enzyme is most active?  A. aspartate is protonated; lysine is deprotonated B. both residues are deprotonated C. aspartate is deprotonated; lysine is protonated D. both residues are protonated

Amino acids that potentially can participate in acid-base catalysis in an enzyme active site, by accepting or donating a proton, can be:   a. Asp, His, Lys   b. Ala, Gly, Val   c. Asp, Gly, Val   d. Ala, Ile, Gly

Which of the following statements is not true about enzymes?* A. Enzymes are biological catalysts B. Enzymes as catalysts lowers the activation energy thus, speeds up the rate of reaction C. Enzymes are proteins D. Enzymes are highly specific E. None of the given options